1. Field
Embodiments of the disclosure relate generally to the field of ducted fan engines and more particularly to embodiments for integral central blading in the fan for secondary air ducting.
2. Background
Ducted fan engines provide high bypass ratios for an efficient propulsion system for air vehicles. By nature, the fan element provides thrust using air displaced through the nacelle or duct surrounding the fan. In most cases, the motive element for the fan, a reciprocating engine or turbojet core is axially aligned with the fan and the fan airflow is directed around the engine or core. Configurations with tractor or pusher style fan/engine integrations may be employed.
Use of a tractor style engine and fan arrangement may be particularly beneficial where integration of the engine and fan in a blended wing body configuration is desired. In certain applications, airflow in addition to the thrust flow created by the fan is required for operational requirements of the engine. Ducting of flow directly from the thrust fan may result in undesirable losses or aerodynamic inefficiencies.
Other turbine engine applications including generators and pumps as well as large turbine or bladed flow devices such as water turbines and wind turbines may additionally require multiple flow paths for the working fluid.
It is therefore desirable to provide a fan having multiple airflow paths to accommodate secondary flow requirements.